1. Field of the Invention
The present invention relates to a positioning method and a positioning system, and in particular, to a method and a system for accurately indoor positioning.
2. Description of Related Art
The global positioning system (GPS) is constructed by satellites in space, the monitoring stations on the ground and the GPS receiver of the user end. Since the GPS positioning is implemented based on the triangulation positioning theory, at least three satellites are required in positioning the GPS receiver of user end. In other words, as long as the user is in the region with the satellite signal reception, the user can utilize the GPS to obtain the positioning data and the navigation data.
When the GPS receiver of the user end is located in the indoor environment, such as being inside the building, since the satellite signal is blocked by the building, the data for positioning is not enough for implementing the positioning. In order to solve the problem mentioned above, the positioning techniques, such as infrared positioning, Bluetooth positioning and wireless sensor positioning, adopted for indoor positioning are developed.
As for the infrared positioning technique, since the light cannot pass through the blocks, the infrared positioning technique has the disadvantages of short straight-line view distance and short transmission distance. The Bluetooth positioning technique is limited by the complexity of the environment. Once the environment is too complex, the stability of the Bluetooth system is getting worse. The wireless sensor positioning technique including methods of time-of-arrival (TOA), time-difference-of-arrival (TDOA), angle-of-arrival (AOA) and signal-strength-ranging (SSR) is used for indoor ranging and positioning. However, in the aforementioned ranging methods, the fact that the signal is affected by the non-line-of-sight (NLOS) transmission easily leads to the inaccurate positioning result. Moreover, when the number of the positioning target is over mass, the large TOA ranging will lead to the congested wireless network.